In-Situ Deposition and Densification Treatment for Metal-Comprising Resist Layer

ABSTRACT

Metal-comprising resist layers (for example, metal oxide resist layers), methods for forming the metal-comprising resist layers, and lithography methods that implement the metal-comprising resist layers are disclosed herein that can improve lithography resolution. An exemplary method includes forming a metal oxide resist layer over a workpiece by performing deposition processes to form metal oxide resist sublayers of the metal oxide resist layer over the workpiece and performing a densification process on at least one of the metal oxide resist sublayers. Each deposition process forms a respective one of the metal oxide resist sublayers. The densification process increases a density of the at least one of the metal oxide resist sublayers. Parameters of the deposition processes and/or parameters of the densification process can be tuned to achieve different density profiles, different density characteristics, and/or different absorption characteristics to optimize patterning of the metal oxide resist layer.

The present application is a divisional application of U.S. patentapplication Ser. No. 17/231,702, filed Apr. 15, 2021, which is anon-provisional application of and claims benefit of U.S. ProvisionalPatent Application Ser. No. 63/085,610, filed Sep. 30, 2020, the entiredisclosures of which are incorporated herein by reference.

BACKGROUND

Lithography processes are extensively utilized in integrated circuit(IC) manufacturing, where various IC patterns are transferred to aworkpiece to form an IC device. A lithography process typically involvesforming a resist layer over the workpiece, exposing the resist layer topatterned radiation, and developing the exposed resist layer, therebyforming a patterned resist layer. The patterned resist layer is used asa masking element during subsequent IC processing, such as an etchingprocess, where a resist pattern of the patterned resist layer istransferred to the workpiece. A quality of the resist pattern directlyimpacts a quality of the IC device. As IC technologies continuallyprogress towards smaller technology nodes (for example, down to 14nanometers, 10 nanometers, and below), line edge roughness (LER), linewidth roughness (LWR), and/or critical dimension uniformity (CDU) of theresist pattern has become critical. Multiple factors affect LER, LWR,and/or CDU of the resist pattern, among which are absorptioncharacteristics (e.g., ability to absorb radiation) and/or outgas singcharacteristics (e.g., propensity to release contamination) of theresist layer. Although existing resist layers and techniques for formingthe resist layers have been generally adequate for their intendedpurposes, they have not been entirely satisfactory in all respects andimprovements are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1A illustrates lithography processes that use metal oxide resistlayers to improve lithography pattern fidelity according to variousaspects of the present disclosure.

FIG. 1B illustrates a cyclic metal resist deposition process for formingthe metal oxide resist layers of FIG. 1A according to various aspects ofthe present disclosure.

FIG. 1C illustrates top views of the metal oxide resist layers of FIG.1A after deposition and after patterning according to various aspects ofthe present disclosure.

FIG. 2A illustrates different lithography processes that use metal oxideresist layers to improve lithography pattern fidelity according tovarious aspects of the present disclosure.

FIG. 2B illustrates a cyclic metal resist deposition process for formingthe metal oxide resist layers of FIG. 2A according to various aspects ofthe present disclosure.

FIG. 3A illustrates different lithography processes that use metal oxideresist layers to improve lithography pattern fidelity according tovarious aspects of the present disclosure.

FIG. 3B illustrates a cyclic metal resist deposition process for formingthe metal oxide resist layers of FIG. 3A according to various aspects ofthe present disclosure.

FIG. 4 illustrates a cyclic metal resist deposition process for forminga metal oxide resist layer according to various aspects of the presentdisclosure.

FIG. 5 illustrates a cyclic metal resist deposition process for forminga metal oxide resist layer according to various aspects of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure relates generally to methods for manufacturingintegrated circuit (IC) devices, and more particularly, to lithographytechniques and/or lithography materials implemented during manufacturingof IC devices.

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,spatially relative terms, for example, “lower,” “upper,” “horizontal,”“vertical,” “above,” “over,” “below,” “beneath,” “up,” “down,” “top,”“bottom,” etc. as well as derivatives thereof (e.g., “horizontally,”“downwardly,” “upwardly,” etc.) are used for ease of the presentdisclosure of one features relationship to another feature. Thespatially relative terms are intended to cover different orientations ofthe device including the features. Furthermore, when a number or a rangeof numbers is described with “substantially,” “about,” “approximate,”and the like, the term is intended to encompass numbers that are withina reasonable range considering variations that inherently arise duringmanufacturing as understood by one of ordinary skill in the art. Forexample, the number or range of numbers encompasses a reasonable rangeincluding the number described, such as within +/−10% of the numberdescribed, based on known manufacturing tolerances associated withmanufacturing a feature having a characteristic associated with thenumber. For example, a material layer having a thickness of “about 5 nm”can encompass a dimension range from 4.5 nm to 5.5 nm wheremanufacturing tolerances associated with depositing the material layerare known to be +/−10% by one of ordinary skill in the art. Stillfurther, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Lithography processes are extensively utilized in IC manufacturing,where various IC patterns are transferred to a workpiece to form an ICdevice. A lithography process involves forming a resist layer over aworkpiece and exposing the resist layer to patterned radiation. Afterexposed to the patterned radiation, the resist layer is developed in adeveloper (in other words, a chemical solution). The developer removesportions of the resist layer (for example, exposed portions of positivetone resist layers or unexposed portions of negative tone resistlayers), thereby forming a patterned resist layer. The patterned resistlayer is then often used as a masking element during a subsequentprocess, such as an etching process or an implantation process, totransfer a pattern in the patterned resist layer (referred to herein asa resist pattern) to the workpiece. Advanced lithography materials, suchas chemically amplified resist (CAR) materials, have been introduced toimprove sensitivity (S) of the resist layer to the radiation, therebymaximizing utilization of the radiation. Sensitivity generallycorresponds with an amount of incident radiation (amount of energy perunit area) required to produce sufficient chemical reactions to define apattern in a resist layer. For example, CAR materials can generatemultiple chemical reactions upon exposure to radiation, therebychemically amplifying a response to the radiation, which reducessensitivity and thus lowers exposure doses needed to define a resistpattern. CAR materials typically include a polymer that is resistant toan IC process (e.g., an etching process), an acid generating component(e.g., a photoacid generator (PAG)), and a solvent component. The PAGgenerates acid upon exposure to radiation, which functions as a catalystfor causing chemical reactions that decrease (or increase) solubility ofexposed portions of a resist layer. For example, acid generated from thePAG catalyzes crosslinking of the polymer, thereby reducing solubilityof the exposed portions.

While CAR materials are configured to reduce sensitivity, CAR materialsmust also satisfy other resist performance characteristics, such asresolution (R), resist contrast, and roughness. Resolution generallydescribes an ability of a resist material to print (image) a minimumfeature size with acceptable quality and/or control, where resistcontrast, resist thickness loss, proximity effects, swelling and/orcontraction of the resist material (typically caused by development),and/or other resist characteristics and/or lithography characteristicscontribute to the resolution. Resist contrast generally refers to anability of a resist material to distinguish between light (exposed)regions and dark (unexposed) regions, where resist materials with highercontrasts provide better resolution, resist profiles, and/or roughness.Roughness, such as line edge roughness (LER) and/or line width roughness(LWR), generally describes whether a pattern in a resist layer includesedge variations, width variations, critical dimension variations, and/orother variations. For example, LER generally describes deviations inedges of a line, whereas LWR generally describes deviations in a widthof the line, such as from a critical dimension (CD) width for the line.Improving one resist performance characteristic (for example, reducingLER) often comes at the expense of degrading another resist performancecharacteristic (for example, increasing sensitivity), such that attemptsat simultaneously minimizing resolution, LER, and sensitivity is oftenreferred to as RLS tradeoff. Overcoming the RLS tradeoff presentschallenges to meeting lithography process demands for advanced ICtechnology nodes, which have continually smaller feature sizes, and thusrequire ever-shrinking resist pattern dimensions and finer lithographyresolution.

Extreme ultraviolet (EUV) lithography, which utilizes radiation havingwavelengths in the EUV range, provides promise for meeting finerlithography resolution limits, particularly for sub-10 nm ICmanufacturing. However, higher sensitivity CAR materials are oftenrequired at EUV wavelengths because exposure doses required for meetingresolution, contrast, and/or LER requirements, along with throughputrequirements (such as wafers per hour (WPH)), are limited byconventional EUV sources. For example, since a number of photonsabsorbed by a volume of a resist material is proportional to wavelengthand an amount of absorbed energy is proportional to exposure dose, atotal absorbed energy is discretized into fewer photons as wavelengthdecreases. A volume of resist material thus absorbs fewer EUV photonsthan DUV photons when exposed to the same exposure dose, which oftenmeans that less acid will be generated by CAR materials for catalyzingreactions. Such phenomenon is generally referred to as shot noise.Though increasing EUV exposure dose can alleviate the shot noise,thereby improving resolution, contrast, and/or roughness, such isachieved by increasing EUV source power or decreasing scan speed (inother words, decreasing throughput, such as WPH). Since current EUVsources have limited ability to meet the high-power EUV sourcerequirements for CAR materials and decreasing throughput is not a viableoption for meeting next generation IC manufacturing requirements, metaloxide resist materials that exhibit sufficient sensitivity to radiationwhile still meeting other RLS characteristics, such as resolution andLER, are being explored as potential replacements for CAR materials inEUV lithography.

Metal oxide resist materials have been observed to exhibit better EUVabsorption characteristics (e.g., metal oxide resist materials canabsorb more EUV photons than CAR materials), better LER/LWRcharacteristics (e.g., metal oxide resist materials are often lesssusceptible to secondary electron exposure and/or acid amplificationeffects that cause resist blur in CAR materials), and better etchingcharacteristics than CAR materials (e.g., metal oxide resist materialsachieve greater etching selectivity when used as an etch mask comparedto CAR materials). The present disclosure explores deposition techniquesfor further improve patterning characteristics of metal oxide resistmaterials. For example, the present disclosure recognizes that metaloxide resist materials formed by conventional deposition techniques haverandom, loose, and often, non-ordered, non-dense, and/or non-uniformatomic structures, which can diminish LER/LWR and patterning uniformity.Further, such atomic structures can lead to undesirable outgassing thatcan contaminate work pieces being processed using the metal oxide resistmaterials and/or contaminate process tools used to process (e.g.,deposit, expose, develop, etc.) the metal oxide resist materials. Thepresent disclosure thus proposes methods for forming metal oxide resistmaterials having atomic structures that are less random, loose, and moreordered, dense, and/or uniform than metal oxide resist materials formedusing conventional deposition techniques. The disclosed methods includeperforming a cyclic deposition process to form metal oxide resistsublayers that combine to form a metal oxide resist layer and performinga densification process that increases a density of at least one of themetal oxide resist sublayers. The deposition process and thedensification process can be performed in a same process chamber (i.e.,in-situ). Parameters of the deposition process and/or the densificationprocess are tuned to achieve uniform densities or different densities inthe metal oxide resist sublayers, thereby providing different densityprofiles. In some embodiments, a densification process is performedbefore the deposition process, for example, to enhance adhesion of themetal oxide resist layer to a workpiece. Metal oxide resist layersformed as described by the present disclosure can reduce outgassing,improve LER/LWR, and/or improve pattern uniformity across a wafer.Different embodiments disclosed herein offer different advantages and noparticular advantage is necessarily required in all embodiments.

Turning to FIGS. 1A-1C, FIG. 1A illustrates lithography processes, suchas a lithography process A and a lithography process B, that use metaloxide resist layers to improve lithography pattern fidelity according tovarious aspects of the present disclosure, FIG. 1B illustrates a cyclicmetal resist deposition process A used to form the metal oxide resistlayer in lithography process B according to various aspects of thepresent disclosure, and FIG. 1C illustrates top views of workpiecesafter deposition and after patterning of the metal oxide resist layersused in lithography process A and lithography process B according tovarious aspects of the present disclosure. In FIGS. 1A-1C, a workpiece10, in portion or entirety, is depicted at an intermediate stage offabrication of an IC device, where workpiece 10 undergoes lithographyprocess A or lithography process B. In some embodiments, the IC deviceis a microprocessor, a memory, and/or other IC device, or portionthereof. Workpiece 10 can be a portion of an IC chip, a system on chip(SoC), or portion thereof, that includes various passive and activemicroelectronic devices, such as resistors, capacitors, inductors,diodes, p-type field effect transistors, n-type field effecttransistors, metal-oxide semiconductor field effect transistors,complementary metal-oxide semiconductor transistors, bipolar junctiontransistors, laterally diffused metal-oxide semiconductor transistors,high voltage transistors, high frequency transistors, fin-like fieldeffect transistors, gate-all-around transistors, other suitable ICcomponents, or combinations thereof. FIGS. 1A-1C have been simplifiedfor the sake of clarity to better understand the inventive concepts ofthe present disclosure. Additional features can be added in workpiece10, lithography process A, lithography process B, and/or cyclic metalresist deposition process A, and some of the features described belowcan be replaced, modified, or eliminated in other embodiments ofworkpiece 10, lithography process A, lithography process B, and/orcyclic metal resist deposition process A.

In FIGS. 1A-1C, workpiece 10 includes a wafer 15 and a material layer 20to be processed (also referred to herein as an underlying layer)disposed over wafer 15. Wafer 15 includes a substrate (for example, asemiconductor substrate), a mask (also referred to as a photomask orreticle), or any base material on which processing may be conducted toprovide layers of material to form various features of an IC device.Depending on IC fabrication stage, wafer 15 includes various materiallayers (for example, dielectric layers, semiconductor layers, and/ormetal layers) configured to form IC features (for example, n-wells,p-wells, isolation structures (for example, shallow trench isolationstructures and/or deep trench isolation structures), source/drainfeatures (including epitaxial source/drain features), metal gates and/ordummy gates, gate spacers, source/drain contacts, gate contacts, vias,metal lines, other IC features, or combinations thereof). In someembodiments, material layer 20 is a semiconductor layer including, forexample, silicon, germanium, silicon germanium, other suitablesemiconductor constituent, or combinations thereof. In some embodiments,material layer 20 is a metal layer including, for example, titanium,aluminum, tungsten, tantalum, copper, cobalt, ruthenium, alloys thereof,other suitable metal constituent and/or alloys thereof, or combinationsthereof. In some embodiments, material layer 20 is a dielectric layerincluding, for example, silicon, metal, oxygen, nitrogen, carbon, othersuitable dielectric constituent, or combinations thereof. In someembodiments, material layer 20 is a hard mask layer to be patterned foruse in subsequent processing of workpiece 10. In some embodiments,material layer 20 is an anti-reflective coating (ARC) layer. In someembodiments, material layer 20 is a layer to be used for forming a gatefeature, such as a gate dielectric and/or a gate electrode, asource/drain feature, such as an epitaxial source/drain, and/or aninterconnect feature, such as a conductive structure or a dielectriclayer of a multilayer interconnect of workpiece 10. In some embodiments,where workpiece 10 is fabricated into a mask for patterning IC devices,wafer 15 is a mask substrate that includes a transparent material and/ora low thermal expansion material (e.g., glass, quartz, silicon oxidetitanium, and/or other suitable material) and material layer 20 is alayer to be processed to form an IC pattern therein, such as an absorberlayer (for example, material layer 20 includes chromium). The presentdisclosure contemplates embodiments where material layer 20 is omittedfrom workpiece 10 and wafer 15 is directly processed and embodimentswhere material layer 20 includes more than one material layer.

Both lithography process A and lithography process B begin withdepositing a metal oxide resist layer having a target thickness T overmaterial layer 20, such as a metal oxide resist layer 30 in lithographyprocess A and a metal oxide resist layer 40 in lithography process B.Metal oxide resist layer 30 and metal oxide resist layer 40 are bothsensitive to radiation used during a lithography exposure process, suchas deep ultraviolet (DUV) radiation, EUV radiation, e-beam radiation,ion beam radiation, and/or other suitable radiation. In someembodiments, metal oxide resist layer 30 and metal oxide resist layer 40are sensitive to radiation having a wavelength less than about 13.5 nm.Metal oxide resist layer 30 and metal oxide resist layer 40 each includea metal-and-oxygen comprising radiation sensitive material, where themetal is hafnium, titanium, zirconium, tantalum, tin, lanthanum, indium,antimony, other metal constituent that facilitates absorption ofradiation (e.g., EUV radiation) and/or resistance to an IC process usedduring fabrication of workpiece 10 (e.g., etching), or combinationsthereof. In some embodiments, metal oxide resist layer 30 and/or metaloxide resist layer 40 can include other resist components thatfacilitate absorption of radiation and/or crosslinking reactions uponexposure to radiation, such as photoacid generator (PAG) component,thermal acid generator (TAG) component, photo-decomposable base (PDB)component, other suitable resist component, or combinations thereof. Insome embodiments, before depositing metal oxide resist layer 30 and/ormetal oxide resist layer 40, an ARC layer is formed over material layer20, such that metal oxide resist layer 30 and/or metal oxide resistlayer 40 are deposited on the ARC layer. The ARC layer may be anitrogen-free ARC (NFARC) layer that includes silicon oxide, siliconoxycarbide, other suitable material, or combinations thereof. In someembodiments, more than one layer (including one or more ARC layers) canbe formed between material layer 20 and metal oxide resist layer 30and/or metal oxide resist layer 40. Metal oxide resist layer 30 and/ormetal oxide resist layer 40 are also referred to as metal resist layers,photosensitive metal layers, metal imaging layers, metal patterninglayers, and/or radiation sensitive metal layers.

Metal oxide resist layer 30 and metal oxide resist layer 40 are formedby different deposition processes, which results in metal oxide resistlayer 30 and metal oxide resist layer 40 having differentcharacteristics that impact pattern fidelity. In lithography process A,metal oxide resist layer 30 is blanket deposited over material layer 20by a chemical vapor deposition (CVD) process. In some embodiments, theCVD process includes loading workpiece 10 having material layer 20disposed over wafer 15 in a process chamber, heating workpiece 10 to adesired temperature (e.g., a temperature that facilitates chemicalreactions needed to form metal-and-oxygen comprising resist materialover material layer 20), flowing one or more precursors and/or carriersinto the process chamber, where the precursors react and/or decompose toform a metal-and-oxygen comprising resist material over material layer20, and purging any remaining precursors (e.g., unreacted precursors),carriers, and/or byproducts from the process chamber. Themetal-and-oxygen comprising resist material accumulates on materiallayer 20, and the CVD process is performed until the metal-and-oxygencomprising resist material accumulated over material layer 20 has targetthickness T. During the CVD process, the precursors can react with oneanother, material layer 20, metal-and-oxygen comprising resist materialaccumulating on material layer 20, and/or byproducts of chemicalreactions thereof to form metal oxide resist layer 30. In someembodiments, the CVD process is a plasma enhanced CVD (PECVD), remotePECVD (RPECVD) process, a metal-organic CVD (MOCVD) process, alow-pressure CVD (LPCVD) process, ultrahigh vacuum CVD (UHVCVD) process,a sub-atmospheric pressure CVD (SACVD) process, a laser-assisted CVD(LACVD) process, an aerosol-assisted CVD (AACVD) process, atomic layerCVD (ALCVD), other suitable CVD process, or combinations thereof. Insome embodiments, metal oxide resist layer 30 having thickness T isblanket deposited over material layer 20 by an atomic layer deposition(ALD) process, a physical vapor deposition (PVD) process, or othersuitable deposition process.

Because chemical reactions during the CVD process are random and/orincomplete, it has been observed that metal oxide resist layer 30 mayexhibit a random, loose, and often, non-ordered, non-dense, and/ornon-uniform atomic structure that can diminish patterning uniformity.For example, an atomic structure of metal oxide resist layer 30 includesrandomly stacked, loosely packed metal atoms, oxygen atoms, single metaloxide molecules (Me₁O_(x), where x is a number of oxygen atoms), and/ormetal oxide clusters (Me_(y)O_(z), where y is a number of metal atomsand z is a number of oxygen atoms), which can collectively be referredto as metal-and-oxygen constituents MeO. Metal-and-oxygen constituentsMeO may not have an ordered arrangement (e.g., a repeating pattern ofmetal-and-oxygen constituents MeO), which can lead to metal oxide resistlayer 30 having disparate clusters of metal-and-oxygen constituents MeOand thus a non-uniform density (e.g., an amount of metal-and-oxygenconstituents MeO in one portion of metal oxide resist layer 30 isdifferent than an amount of metal-and-oxygen constituents MeO inanother, similarly sized portion of metal oxide resist layer 30). Sincean amount of radiation that a material can absorb depends on its densityand metal oxide resist layer 30 has a non-uniform density, metal oxidelayer 30 may absorb radiation non-uniformly, which diminishes LER/LWRachievable by patterning metal oxide layer 30 (e.g., patterned metaloxide layer 30 exhibits larger than desirable LER/LWR and degraded linewidth and/or line edge uniformity) and/or requires larger exposure dosesto ensure sufficient and/or uniform absorption of radiation to improveLER/LWR. Further, the random arrangement of metal-and-oxygenconstituents MeO can lead to vacancies and/or dislocations (V) formingwithin the atomic structure of metal oxide resist layer 30, andincomplete chemical reactions during the CVD process can lead tometal-and-oxygen constituents MeO that are not connect to (bonded with)any other metal-and-oxygen constituents MeO of metal oxide resist layer30, such as depicted in FIG. 1A. These “loose” metal-and-oxygenconstituents MeO and/or weakly bonded metal-and-oxygen constituents MeOmay outgas (i.e., escape from metal oxide resist layer 30 into anambient of the process chamber) during subsequent processing, which cancontaminate workpiece 10 and/or the process chamber. Outgassedmetal-and-oxygen constituents MeO may cause film defects, for example,by scratching and/or peeling metal oxide resist layer 30, material layer20 and/or wafer 15. Further, as multiple wafers are processed to formmetal oxide resist layers, such as metal oxide resist layers 30, in aprocess chamber, pattern fidelity worsens over time as outgascontamination accumulates in the process chamber.

To address such issues, the present disclosure proposes cyclic metaloxide resist deposition processes that provide metal oxide resist layersthat are denser than and absorb radiation better than metal oxide resistlayer 30, such that lower exposure doses can be implemented to patternthe metal oxide resist layers and still achieve uniform absorption ofradiation to improve LER/LWR. The denser metal oxide resist layers alsoexhibit less outgassing than metal oxide resist layer 30. In someembodiments, atomic structures of metal oxide resist layers formed bythe proposed cyclic metal oxide resist deposition processes includemetal-and-oxygen constituents stacked in an ordered arrangement (e.g., arepeating pattern of metal-and-oxygen constituents). In someembodiments, atomic structures of metal oxide resist layers formed bythe proposed cyclic metal oxide resist deposition processes have lessvacancies and/or less incomplete metal-and-oxygen bonds (and, in someembodiments, are substantially free of vacancies and/or incompletemetal-and-oxygen bonds) compared to metal oxide resist layer 30. In someembodiments, clusters of metal-and-oxygen constituents are distributeduniformly in metal oxide resist layers formed by the proposed cyclicmetal oxide resist deposition processes, such that metal oxide resistlayers formed by the proposed cyclic metal oxide resist depositionprocesses have substantially uniform densities (e.g., amounts ofmetal-and-oxygen constituents in different, similarly sized portions ofthe metal oxide resist layers are substantially the same). In someembodiments, a concentration of metal oxide clusters, a metalconcentration, an oxygen concentration, and/or a metal oxideconcentration in the proposed metal oxide resist layers increases ordecreases from top surfaces to bottom surfaces of the metal oxide resistlayers to achieve gradient density characteristics (e.g., a density thatincreases or decreases from the top surfaces to the bottom surfaces ofthe metal oxide resist layers). In some embodiments, a concentration ofmetal oxide clusters, a metal concentration, an oxygen concentration,and/or a metal oxide concentration in the proposed metal oxide resistlayers is different at different depths to achieve desired densitycharacteristics, such as those described herein. In some embodiments,the proposed metal oxide resist layers can include 12-MeO_(x) clusters,8-MeO_(x) clusters, 6-MeO_(x) clusters, 4-MeO_(x) clusters,dimer-MeO_(x) clusters, and/or mono-MeO_(x) clusters depending ondesired density characteristics, such as those described herein.

Turning to lithography process B, a cyclic metal resist depositionprocess A forms metal oxide resist layer 40 having a substantiallyuniform density from bottom to top, such as from a bottom surface ofmetal oxide layer 40 (e.g., interfacing with material layer 20) to a topsurface of metal oxide resist layer 40. The density of metal oxideresist layer 40 is greater than the density of metal oxide resist layer30, such that metal oxide resist layer 40 can absorb more radiation thanmetal oxide resist layer 30 when exposed to the same exposure dose andabsorb such radiation more uniformly than metal oxide resist layer 30.For example, cyclic metal resist deposition process A forms a metaloxide resist sublayer 40A, a metal oxide resist sublayer 40B, a metaloxide resist sublayer 40C, and a metal oxide resist sublayer 40D, whichcombine to form metal oxide resist layer 40 having thickness T. Metaloxide resist sublayers 40A-40D respectively have a thickness t1, athickness t2, a thickness t3, and a thickness t4, where a sum ofthickness t1, thickness t2, thickness t3, and thickness t4 is equal totarget thickness T. A density of metal oxide resist sublayer 40A, adensity of metal oxide resist sublayer 40B, a density of metal oxideresist sublayer 40C, and a density of metal oxide resist sublayer 40Dare substantially the same. In the depicted embodiment, densities ofmetal oxide resist sublayers 40A-40D are all greater than the density ofmetal oxide resist layer 30. In the depicted embodiment, thickness t1,thickness t2, thickness t3, and thickness t4 are substantially the same.In some embodiments, thickness t1, thickness t2, thickness t3, and/orthickness t4 are different or the same depending on desired densityprofile and/or density characteristics.

Turning to FIG. 1B, cyclic metal resist deposition process A includesfour cycles, where each cycle forms one of metal oxide resist sublayers40A-40D and each cycle includes a deposition process and a densificationprocess. For example, cyclic metal resist deposition process A includesa cycle 1, a cycle 2, a cycle 3, and a cycle 4 (alternatively referredto as phases 1-4). Cycle 1 includes performing a deposition process 50-1to form a metal oxide resist sublayer 40A′ having thickness t1 and afirst density on material layer 20 and performing a densificationprocess 52-1 on metal oxide resist sublayer 40A′, thereby forming metaloxide resist sublayer 40A having a second density greater than the firstdensity. Cycle 2 includes performing a deposition process 50-2 to form ametal oxide resist sublayer 40B′ having thickness t2 and a third densityon metal oxide resist sublayer 40A and performing a densificationprocess 52-2 on metal oxide resist sublayer 40B′, thereby forming metaloxide resist sublayer 40B having a fourth density greater than the thirddensity. Cycle 3 includes performing a deposition process 50-3 to form ametal oxide resist sublayer 40C′ having thickness t3 and a fifth densityon metal oxide resist sublayer 40B and performing a densificationprocess 52-3 on metal oxide resist sublayer 40C′, thereby forming metaloxide resist sublayer 40C having a sixth density greater than the fifthdensity. Cycle 4 includes performing a deposition process 50-4 to form ametal oxide resist sublayer 40D′ having thickness t4 and a seventhdensity on metal oxide resist sublayer 40C and performing adensification process 52-4 on metal oxide resist sublayer 40D′, therebyforming metal oxide resist sublayer 40D having an eight density greaterthan the seventh density. In the depicted embodiment, the seconddensity, the fourth density, the sixth density, and the eighth density(i.e., densities after densification processes 52-1-52-4) aresubstantially the same, such that metal oxide resist layer 40 has asubstantially uniform density from bottom to top. In some embodiments,the first density, the third density, the fifth density, and the seventhdensity (i.e., densities of as-deposited metal-and-oxygen comprisingresist materials) are substantially the same. In some embodiments, thefirst density, the third density, the fifth density, and/or the seventhdensity are the same as a density of metal oxide resist layer 30. Insome embodiments, the first density, the third density, the fifthdensity, and/or the seventh density are different. In some embodiments,densification processes 52-1-52-4 may reduce thickness t1, thickness t2,thickness t3, and/or thickness t4, respectively, such that thicknesst1-t4 of as-deposited metal oxide resist sublayers 40A′-40D′,respectively, are greater than thicknesses t1-t4 of metal oxide resistsublayers 40A-40D, respectively.

In some embodiments, deposition processes 50-1-50-4 are CVD processes.In some embodiments, deposition processes 50-1-50-4 are ALD processes.After loading workpiece 10 having material layer 20 disposed over wafer15 in a process chamber, each deposition processes 50-1-50-4 can includeheating workpiece 10 to a desired temperature (e.g., a temperature thatfacilitates chemical reactions needed to form metal-and-oxygencomprising resist material over material layer 20), flowing one or moredeposition precursors and/or carriers into the process chamber, wherethe deposition precursors react and/or decompose to form ametal-and-oxygen comprising resist material over material layer 20, andpurging any remaining deposition precursors (e.g., unreacted depositionprecursors), carriers, and/or byproducts from the process chamber. Eachdeposition processes 50-1-50-4 has at least one deposition phase and atleast one purge phase. The metal-and-oxygen comprising resist materialaccumulates on material layer 20 during the deposition phase, and thedeposition phase is performed until the metal-and-oxygen comprisingresist material accumulated over material layer 20 has thickness t1,thickness t2, thickness t3, or thickness t4 depending on cycle number.During the deposition phase, the deposition precursors can react withone another, material layer 20, metal-and-oxygen comprising resistmaterial accumulating on material layer 20, and/or byproducts ofchemical reactions thereof to form metal oxide resist sublayers 40A-40D.In some embodiments, the deposition precursors include ametal-containing precursor, a reaction gas, and/or a carrier. In someembodiments, the metal-containing precursor includes M_(a)R_(b)X_(c),where 1≤a≤2, b≥1, and c≥1. In some embodiments, b+c≤5. In someembodiments, M is Sn, Bi, Sb, In, Te, Ti, Zr, Hf, V, Co, Mo, W, Al, Ga,Si, Ge, P, As, Y, La, Ce, or Lu. In some embodiments, R is a substitutedalkyl group, a substituted alkenyl group, a substituted carboxylategroup, an unsubstituted alkyl group, an unsubstituted alkenyl group, oran unsubstituted carboxylate group. In some embodiments, X is a halidegroup or a sulfonate group. In some embodiments, the reaction gasincludes amine, water, ozone, hydrogen peroxide, other suitable reactiongas constituents, or combinations thereof. In some embodiments, thecarrier gas includes argon (e.g., Ar), helium (e.g., He), nitrogen(e.g., N₂), other suitable carrier gas constituent, or combinationsthereof. In some embodiments, a flow rate of a deposition precursor isabout 10 sccm to about 1,000 sccm. In some embodiments, a flow rate of acarrier is about 100 sccm to about 10,000 sccm. In some embodiments, apower is applied to a deposition precursor to generate a plasma, such asa power of about 10 W to about 1,000 W. In some embodiments, the plasmais generated by a radio frequency (RF) power source, such that the poweris RF power. In some embodiments, a duration of the deposition phase isabout 3 seconds to about 3,600 seconds. In some embodiments, a pressuremaintained in the process chamber during the deposition phase is about0.1 torr to about 150 torr. In some embodiments, a temperaturemaintained in the process chamber during the deposition phase is about25° C. to about 300° C. In some embodiments, the purge phase can includeflowing an inert gas (e.g., an argon-containing gas, a helium-containinggas, other suitable inert gas, or combinations thereof) into the processchamber. In some embodiments, a flow rate of the inert gas is about 100sccm to about 10,000 sccm. In some embodiments, a duration of the purgephase is about 3 seconds to about 1,000 seconds. In some embodiments, apressure maintained in the process chamber during the purging phase isabout 10 torr to about 760 torr. In some embodiments, a temperaturemaintained in the process chamber during the purge phase is about 25° C.to about 300° C. In some embodiments, deposition processes 50-1-50-4 arethe same. In some embodiments, deposition processes 50-1-50-4 aredifferent. In some embodiments, deposition processes 50-1-50-4 are anycombination of deposition processes for achieving desired densityprofile and/or density characteristics of metal oxide resist layer 40.

Densification processes 52-1-52-4 include a treatment phase, whichsubjects workpiece 10 to a treatment that can densify (i.e., increase adensity of) metal-and-oxygen comprising resist materials, and a purgephase. In some embodiments, the treatment modifies an atomic structureof metal-and-oxygen comprising resist materials, such that the atomicstructure is more ordered and/or more closely packed after thetreatment. For example, the treatment rearranges metal atoms and/oroxygen atoms of the metal-and-oxygen comprising resist materials, suchthat the metal-and-oxygen comprising resist materials have an orderedarrangement of metal atoms and/or oxygen atoms after the treatmentand/or have less spacing between metal atoms and/or oxygen atoms afterthe treatment. In some embodiments, the treatment strengthensmetal-and-oxygen bonding and/or increases uniformity of metal-and-oxygenbonding in metal-and-oxygen comprising resist materials. For example,the treatment induces chemical reactions, such that partially reactedconstituents of metal-and-oxygen comprising resist materials arecompletely reacted after the treatment and/or unreacted constituents ofmetal-and-oxygen comprising resist materials in the process chamber arepartially reacted or completely reacted after the treatment. In someembodiments, the treatment induces partial crosslinking in themetal-and-oxygen comprising resist materials, which can increasedensities of metal-and-oxygen comprising resist materials. The purgephase removes (purges) any remaining precursors (e.g., unreacteddeposition precursors, unreacted treatment precursors, “loose” reactedprecursors, “loose” metal-and-oxygen constituents, and/or other “loose”reacted constituents), carriers, and/or byproducts from the processchamber, which can further reduce outgassing from metal oxide resistlayer 40 and contamination of workpiece 10 and/or the process chamberarising therefrom compared to metal oxide resist layer 30. In someembodiments, the purge phase includes flowing an inert gas (e.g., anargon-containing gas, a helium-containing gas, other suitable inert gas,or combinations thereof) into the process chamber. In some embodiments,a flow rate of the inert gas is about 100 sccm to about 10,000 sccm. Insome embodiments, a duration of the purge phase is about 3 seconds toabout 600 seconds. In some embodiments, a pressure maintained in theprocess chamber during the purging phase is about 10 torr to about 760torr. In some embodiments, a temperature maintained in the processchamber during the purge phase is about 25° C. to about 300° C.

Example treatments that can increase a density of metal-and-oxygencomprising resist materials and/or achieve modifications to themetal-and-oxygen comprising resist materials as described herein includea plasma densification process, a soft bake process, a UV radiationprocess, an infrared (IR) radiation process, other suitabledensification process, or combinations thereof. In some embodiments,densification processes 52-1-52-4 are the same treatment types (e.g.,densification processes 52-1-52-4 are all plasma densificationprocesses). In some embodiments, densification processes 52-1-52-4 aredifferent treatment types (e.g., densification processes 52-1, 52-4 areplasma densification processes while densification processes 52-1, 52-3are soft bake processes). In some embodiments, densification processes52-1-52-4 are any combination of densification treatments for achievingdesired density profile and/or density characteristics of metal oxideresist layer 40.

In some embodiments, a plasma densification process includes flowing oneor more densification precursors and/or carriers into the processchamber, generating a plasma from the densification precursors, andexposing a metal oxide resist sublayer to the plasma (e.g., bombardingthe metal oxide resist sublayer with the plasma). In some embodiments,the densification precursors include a metal-containing precursor, areaction gas, and/or a carrier. In some embodiments, themetal-containing precursor includes M_(a)R_(b)X_(c), where 1≤a≤2, b≥1,and c≥1. In some embodiments, b+c≤5. In some embodiments, M is Sn, Bi,Sb, In, Te, Ti, Zr, Hf, V, Co, Mo, W, Al, Ga, Si, Ge, P, As, Y, La, Ce,or Lu. In some embodiments, R is a substituted alkyl group, asubstituted alkenyl group, a substituted carboxylate group, anunsubstituted alkyl group, an unsubstituted alkenyl group, or anunsubstituted carboxylate group. In some embodiments, X is a halidegroup or a sulfonate group. In some embodiments, the reaction gasincludes amine, water, ozone, hydrogen peroxide, other suitable reactiongas, or combinations thereof. In some embodiments, a carrier gasincludes argon (e.g., Ar), helium (e.g., He), nitrogen (e.g., N₂), othersuitable carrier gas constituent, or combinations thereof. In someembodiments, a flow rate of a densification precursor is about 10 sccmto about 1,000 sccm. In some embodiments, a flow rate of a carrier isabout 100 sccm to about 10,000 sccm. In some embodiments, a powerapplied to a densification precursor and/or a carrier to generate theplasma is about 10 W to about 1,000 W. In some embodiments, the powerapplied to the densification precursor and/or the carrier to generatethe plasma is lower power, such as less than about 100 W. In someembodiments, the plasma is generated by an RF power source, such thatthe power is RF power. In some embodiments, the metal oxide resistsublayer is exposed to the plasma for about 3 seconds to about 3,600seconds. In some embodiments, a pressure maintained in the processchamber during the plasma densification process is about 0.1 torr toabout 150 torr. In some embodiments, a temperature maintained in theprocess chamber during the plasma densification process is about 25° C.to about 300° C.

In some embodiments, a soft bake process (also referred to as anannealing process and/or a thermal process) heats workpiece 10(including the one or more metal oxide resist sublayers) for a time. Thesoft bake process can apply heat to a front of workpiece 10 (e.g., to atopmost metal oxide resist sublayer of workpiece 10), a bottom ofworkpiece 10 (e.g., to wafer 15), sides of workpiece 10, or combinationsthereof. In some embodiments, the soft bake process heats workpiece 10to a temperature of about 80° C. to about 250° C. In some embodiments,workpiece 10 is baked (annealed) for about 60 seconds to about 300seconds. In some embodiments, a pressure maintained in the processchamber during the soft bake process is about 0.1 torr to about 150torr. In some embodiments, workpiece 10 is baked (annealed) in an inertgas environment (including, for example, argon, helium, and/or otherinert gas constituent) or a reactive gas environment (including, forexample, oxygen, hydrogen, nitrogen, and/or other reactive gasconstituent).

In some embodiments, a UV radiation process exposes one or more metaloxide resist sublayers of workpiece 10 to UV radiation for a time. Insome embodiments, the UV radiation has a wavelength of about 10 nm toabout 400 nm. In some embodiments, the metal oxide resist sublayer isexposed to UV radiation for about 60 seconds to about 3,600 seconds. Insome embodiments, the UV radiation process heats workpiece 10 to atemperature of about 20° C. to about 25° C. In some embodiments, apressure maintained in the process chamber during the UV radiationprocess is about 1×10⁻⁵ torr to about 1×10⁴ torr. In some embodiments,workpiece 10 is treated with UV radiation in an inert gas environment(including, for example, argon, helium, and/or other inert gasconstituent) or a reactive gas environment (including, for example,oxygen, hydrogen, nitrogen, and/or other reactive gas constituent).

In some embodiments, an infrared (IR) radiation process exposes one ormore metal oxide resist sublayers of workpiece 10 to IR radiation for atime. In some embodiments, the IR radiation has a wavelength that isgreater than about 300 nm. In some embodiments, the IR radiation is farinfrared (FIR) radiation having a wavelength, for example, of about 50μm to about 1,000 μm. In some embodiments, the metal oxide resistsublayer is exposed to IR radiation for about 10 seconds to about 600seconds. In some embodiments, the IR radiation process heats workpiece10 to a temperature of about 25° C. to about 250° C. In someembodiments, a pressure maintained in the process chamber during the IRradiation process is about 0.1 torr to about 150 torr. In someembodiments, workpiece 10 is treated with IR radiation in an inert gasenvironment (including, for example, argon, helium, and/or other inertgas constituent) or a reactive gas environment (including, for example,oxygen, hydrogen, nitrogen, and/or other reactive gas constituent).

In some embodiments, a pre-deposition treatment process is performedbefore performing deposition processes 50-1-50-4 to enhance adhesion ofmetal oxide resist layer 40 to material layer 20 and reduce peeling ofmetal oxide resist layer 40 from material layer 20. In some embodiments,the pre-deposition treatment process is combined with deposition process50-1. For example, a deposition phase can include a pre-depositionportion and a deposition portion, where deposition parameters areadjusted during deposition process 50-1 to switch from thepre-deposition portion to the deposition portion, such as depositionprecursor flow rate, power, time, and/or temperature. Depositionparameters of the pre-deposition portion can be tuned to increasechemical reactions (and thus linking and/or bonding) between depositionprecursor and material layer 20 to form a seed metal-and-oxygencomprising material on material layer 20. Deposition parameters of thedeposition portion can be tuned to form metal-and-oxygen comprisingmaterial having density characteristics desired for metal oxide resistsublayer 40A. In such embodiments, the seed metal-and-oxygen comprisingmaterial can form a portion of metal oxide resist sublayer 40A. In someembodiments, the pre-deposition treatment process is a plasma treatmentprocess. The present disclosure contemplates the pre-depositiontreatment process including any treatment that can be performed onworkpiece 10 to increase adhesion of metal oxide resist layer 40thereto.

Deposition processes 50-1-50-4 and densification processes 52-1-52-4 areperformed in-situ. As used herein, the term “in-situ” is used todescribe processes that are performed while a workpiece remains within aprocessing system (e.g., a CVD tool), and where for example, theprocessing system allows the workpiece to remain under vacuumconditions. As such, the term “in-situ” may also generally refer toprocesses in which the workpiece being processed is not exposed to anexternal ambient (e.g., external to the processing system). Subsequentprocessing, such as an exposure process and a development process, maybe performed ex-situ (i.e., workpiece 10 is transferred out of a CVDtool and into an exposure tool and/or a development tool). In thedepicted embodiment, deposition processes 50-1-50-4 and densificationprocesses 52-1-52-4 are performed in a same process chamber of theprocessing system, such as one process chamber of a CVD tool. In someembodiments, deposition processes 50-1-50-4 are performed in a firstprocess chamber of a multi-chamber processing system, densificationprocesses 52-1-52-4 are performed in a second process chamber of themulti-chamber processing system, and workpiece 10 is not exposed toexternal ambient and remains under vacuum while transferred between thefirst process chamber and the second process chamber and within themulti-chamber IC processing system 100 to form metal oxide resist layer40.

Returning to FIG. 1A, after depositing metal oxide resist layer 30 andmetal oxide resist layer 40, lithography process A and lithographyprocess B proceed with exposure processes, which expose metal oxideresist layer 30 and metal oxide resist layer 40 to patterned radiation.In some embodiments, the patterned radiation has a wavelength less thanabout 250 nm, such as DUV radiation, EUV radiation, and/or othersuitable radiation. In the depicted embodiment, the patterned radiationis EUV radiation, such as radiation having a wavelength less than about13.5 nm. In some embodiments, such as depicted, a mask 60 having an ICpattern defined therein is used to provide patterned radiation that canform an image of the IC pattern on metal oxide resist layer 30 and metaloxide resist layer 40. Mask 60 blocks, transmits, and/or reflectsradiation to metal oxide resist layer 30 and metal oxide resist layer 40depending on a mask pattern of mask 60 and/or mask type (for example,binary mask, phase shift mask, or EUV mask). The exposure process can beperformed in air, liquid (immersion lithography), or vacuum (forexample, when exposing workpiece 10 to EUV radiation and/or e-beam). Insome embodiments, the exposure process directly modulates radiation,such as an electron beam (e-beam) or an ion beam, according to an ICpattern without using a mask, such as mask 60.

Since metal oxide resist layer 30 and metal oxide resist layer 40 aresensitive to radiation, latent patterns are formed on metal oxide resistlayer 30 and metal oxide resist layer 40 by the exposure processes.Latent pattern generally refers to a pattern exposed on a resist layer,which becomes a physical resist pattern after the resist layer issubjected to a developing process. In FIG. 1A, the latent pattern ofmetal oxide resist layer 30 includes exposed portions 30E and unexposedportions 30U, and the latent pattern of metal oxide resist layer 40includes exposed portions 40E and unexposed portions 40U. Exposedportions 30E, 40E physically and/or chemically change in response to theexposure process. In the depicted embodiment, the exposure processcauses chemical reactions in exposed portions 30E, 40E that decreasesolubility of exposed portions 30E, 40E to a developer. In someembodiments, exposed portions 30E, 40E are insoluble to the developer.In some embodiments, after the exposure processes, a post-exposurebaking (PEB) process is performed on metal oxide resist layer 30 and/ormetal oxide resist layer 40. The PEB process increases a temperature ofmetal oxide resist layer 30 and/or metal oxide resist layer 40 to about90° C. to about 250° C. Because metal oxide resist layer 40 has a denseand uniform atomic structure while metal oxide resist layer 30 has aloose and random atomic structure (see, for example, top views of metaloxide resist layer 30 and metal oxide resist layer 40 after depositionin FIG. 1C), an exposure dose of patterned radiation projected ontometal oxide resist layer 40 can be less than an exposure dose ofpatterned radiation projected onto metal oxide resist layer 30. In someembodiments, the exposure dose of patterned radiation projected ontometal oxide resist layer 40 can be about 0.1 times less than theexposure dose of patterned radiation projected onto metal oxide resistlayer 30. Further, in contrast to metal oxide resist layer 30, metaloxide resist layer 40 exhibits no (or minimal) outgassing during theexposure process, the PEB process, and/or other subsequent processes,thereby reducing (and, in some embodiments, preventing) film defects inworkpieces caused by outgassing contamination and/or limiting (and, insome embodiments, preventing) reductions in pattern fidelity over timethat arise from outgas contamination accumulating within a processchamber as workpieces are processed to form metal oxide layers.

Lithography process A and lithography process B then each proceed withperforming a developing process on metal oxide resist layer 30 and metaloxide resist layer 40, thereby forming a patterned metal oxide resistlayer 30′ and a patterned metal oxide resist layer 40′, respectively.The developing processes dissolve exposed (or non-exposed) portions ofmetal oxide resist layer 30 and metal oxide resist layer 40 depending oncharacteristics of metal oxide resist layer 30 and metal oxide resistlayer 40, respectively, and characteristics of a developing solutionused in the developing process. In the depicted embodiment, negativetone development (NTD) processes are performed to remove unexposedportions 30U of metal oxide resist layer 30 and unexposed portions 40Uof metal oxide resist layer 40. For example, NTD developers are appliedto metal oxide resist layer 30 and metal oxide resist layer 40 thatdissolve unexposed portions 30U and unexposed portions 40U, leavingpatterned metal oxide resist layer 30′ having openings 62 defined byexposed portions 30E and patterned metal oxide resist layer 40′ havingopenings 64 defined by exposed portions 40E (each of which includesrespective remaining portions of metal oxide resist sublayers 40A-40D).After development, patterned metal oxide resist layer 30′ and patternedmetal oxide resist layer 40′ have resist patterns that corresponds withthe IC pattern of mask 60. Because metal oxide resist layer 40 has adense and uniform structure while metal oxide resist layer 30 has aloose and random structure, metal oxide resist layer 40 absorbspatterned radiation more uniformly than metal oxide resist layer 30, andexposed portions 40E have relatively smooth edges and/or sidewallscompared to exposed portions 30E of metal oxide layer 30. Patternedmetal oxide resist layer 40′ thus exhibits better LER/LWR and criticaldimension uniformity than patterned metal oxide resist layer 30′,significantly enhancing lithography resolution. See, for example, topviews of patterned metal oxide resist layer 30′ and patterned metaloxide resist layer 40′ in FIG. 1C.

The present disclosure further discloses using a cyclic metal resistdeposition process to control density profile and/or densitycharacteristics of a metal oxide resist layer to obtain desiredperformance of the metal oxide resist layer during patterning (i.e.,exposure and development) and optimize particular patterncharacteristics. In some embodiments, a number of cycles (i.e., a numberof metal oxide sublayers), a thickness per cycle (i.e., thicknesses ofthe metal oxide sublayers), a density per cycle (i.e., densities of themetal oxide sublayers), and/or a cycle time can be tuned (adjusted) toachieve desired density profile, desired density characteristics, and/ordesired optimized performance parameters of a metal oxide resist layer.In some embodiments, parameters of the deposition processes, such asdeposition processes 50-1-50-4, are tuned to achieve desired densityprofile, desired density characteristics, and/or desired optimizedperformance parameters of metal oxide resist sublayers. Depositionparameters can include deposition precursor type, deposition precursorflow, deposition pressure, deposition temperature, deposition power,deposition time, other deposition parameter, or combinations thereof. Insome embodiments, parameters of the densification processes, such asdensification processes 52-1-52-3, are tuned to achieve to achievedesired density profile, desired density characteristics, and/or desiredoptimized performance parameters of metal oxide resist sublayers.Densification parameters can include can treatment time, treatmenttemperature, treatment wavelength, treatment power, treatment precursor,treatment precursor flow, other treatment parameter, or combinationsthereof.

Sometimes, during an exposure process, patterned radiation cannotuniformly expose a resist layer along its depth. For example, a top ofthe resist layer receives a higher exposure dose than a bottom of theresist layer. Absorption of exposure photons (e.g., EUV photons) maycorrespondingly decrease from top to bottom of the resist layer, whichreduces crosslinking in the resist layer from top to bottom of theresist layer. This phenomenon may be observed in lithography process A,as depicted in FIG. 2A, where a number of EUV photons (P) at topportions of exposed portions 30E of metal oxide resist layer 30 is morethan a number of EUV photons at bottom portions of exposed portions 30Eof metal oxide resist layer 30. Less chemical reactions (e.g.,crosslinking) thus occur in bottom portions of exposed portions 30Ecompared to top portions of exposed portions 30E, and bottom portions ofexposed portions 30E are partially soluble (instead of insoluble) to adeveloper. As a result, a resist pattern defined by exposed portions 30Eexhibits biases (differences) in top critical dimensions (TCDs) andbottom critical dimensions (BCDs), thereby degrading pattern fidelityprovided by patterned metal oxide resist layer 30′. In some embodiments,such as depicted, exposed portions 30E have tapered sidewalls, wherewidths of exposed portions 30E decrease from top to bottom and TCDs ofexposed portions 30E are greater than BCDs of exposed portions 30E.

Lithography process C implements a cyclic metal resist depositionprocess B to provide a metal oxide resist layer 80 that accounts forsuch phenomenon and optimizes absorption of exposure photons (e.g., EUVphotons) from top to bottom. Metal oxide resist layer 80 has a gradientdensity that decreases from bottom to top, such as from a bottom surfaceof metal oxide layer 80 (e.g., interfacing with material layer 20) to atop surface of metal oxide resist layer 80. For example, cyclic metalresist deposition process B forms a metal oxide resist sublayer 80A, ametal oxide resist sublayer 80B, and a metal oxide resist sublayer 80C,which combine to form metal oxide resist layer 80 having thickness T. Incontrast to metal oxide resist layer 40 (where metal oxide resistsublayers 40A-40D have substantially the same densities), a density ofmetal oxide resist sublayer 80A is greater than a density of metal oxideresist sublayer 80B, and a density of metal oxide resist sublayer 80B isgreater than a density of metal oxide resist sublayer 80C, such thatdensity of metal oxide resist layer 80 decreases from bottom to top.Configuring metal oxide resist layer 80 with a low density top portion(i.e., metal oxide resist sublayer 80C) allows exposure photons to moreeasily pass through metal oxide resist layer 80 to a bottom portion ofmetal oxide layer 80 and thus increases a number of photons that reachthe bottom portion of metal oxide layer 80. Configuring metal oxideresist layer 80 with a high-density bottom portion (i.e., metal oxideresist sublayer 80A) increases absorption of exposure photons by thebottom portion of the metal oxide resist layer 80. The gradient densityof metal oxide resist layer 80 thus increases crosslinking in the bottomportion of the metal oxide resist layer 80. For example, during theexposure process, an amount of chemical reactions (e.g., crosslinking)in bottom portions of exposed portions 80E is substantially the same asan amount of chemical reactions in top portions of exposed portions 80E,such that exposed portions 80E become uniformly insoluble (e.g., fromtop to bottom) to a developer, while unexposed portions 80U remainsoluble to the developer. As a result, after development, a resistpattern is provided by a patterned metal oxide resist layer 80′ havingopenings 82 defined by exposed portions 80E having minimal (to no) biasin TCDs and BCDs (i.e., TCDs are substantially the same as BCDs),thereby improving pattern fidelity. In some embodiments, such asdepicted, exposed portions 80E have substantially parallel sidewalls,and widths of exposed portions 80E are substantially the same from topto bottom. In some embodiments, the low density top portion of metaloxide resist layer 80 has a loose, random, and/or non-uniform atomicstructure and the high-density bottom portion of metal oxide resistlayer 80 has a dense, ordered, and/or uniform atomic structure.

In some embodiments, an overall density (e.g., average density) of metaloxide resist layer 80 is greater than an overall density (e.g., averagedensity) of metal oxide resist layer 30, such that metal oxide resistlayer 80 can absorb more radiation than metal oxide resist layer 30 whenexposed to the same exposure dose and absorb such radiation moreuniformly than metal oxide resist layer 30. In the depicted embodiment,the density of metal oxide resist sublayer 80A and the density of metaloxide resist sublayer 80B are greater than the density of metal oxideresist layer 30, while the density of metal oxide resist sublayer 80C issubstantially the same or less than the density of metal oxide resistlayer 30. In some embodiments, densities of metal oxide resist sublayers80A-80C are all greater than the density of metal oxide resist layer 30.Metal oxide sublayers 80A-80C can have respective density profiles, suchas a substantially uniform density throughout, a gradient density thatincrease or decreases from a bottom surface to a top surface, analternating density, or other suitable density profile. In the depictedembodiment, each of metal oxide sublayers 80A-80C has a substantiallyuniform density. In some embodiments, an atomic structure of metal oxideresist sublayer 80A is more ordered and/or closely packed than an atomicstructure of metal oxide resist sublayer 80B, and an atomic structure ofmetal oxide resist sublayer 80B is more ordered and/or closely packedthan an atomic structure of metal oxide resist sublayer 80C. Metal oxideresist sublayers 80A-80C respectively have a thickness t5, a thicknesst6, and a thickness t7, where a sum of thickness t5, thickness t6, andthickness t7 is equal to target thickness T. In the depicted embodiment,thickness t5, thickness t6, and thickness t7 are substantially the same.In some embodiments, thickness t5, thickness t6, and/or thickness t7 aredifferent and/or the same depending on desired density profile and/ordensity characteristics desired for metal oxide resist layer 80.

FIG. 2B illustrates cyclic metal resist deposition process B accordingto various aspects of the present disclosure. In FIG. 2B, cyclic metalresist deposition process B includes three cycles, where each cycleforms one of metal oxide resist sublayers 80A-80C, each cycle includes adeposition process, and some cycles include a densification process. Forexample, cyclic metal resist deposition process B includes a cycle 1, acycle 2, and a cycle 3. Cycle 1 includes performing a deposition process90-1 to form a metal oxide resist sublayer 80A′ having thickness t5 anda first density on material layer 20 and performing a densificationprocess 92-1 on metal oxide resist sublayer 80A′, thereby forming metaloxide resist sublayer 80A having a second density greater than the firstdensity. Cycle 2 includes performing a deposition process 90-2 to form ametal oxide resist sublayer 80B′ having thickness t6 and a third densityon metal oxide resist sublayer 80A and performing a densificationprocess 92-2 on metal oxide resist sublayer 80B′, thereby forming metaloxide resist sublayer 80B having a fourth density greater than the thirddensity and less than the second density of metal oxide resist sublayer80A. Cycle 3 includes performing a deposition process 90-3 to form metaloxide resist sublayer 80C having a fifth density that is less than thefourth density. No densification process is performed during cycle 3.Deposition processes 90-1-90-3 are similar to deposition processes50-1-50-4 described above, densification processes 92-1,92-2 are similarto densification processes 52-1-52-4, and parameters of depositionprocesses 90-1-90-3 and densification processes 92-1,92-2 can beconfigured to achieve desired density profiles and/or desired densitycharacteristics of metal oxide resist sublayers 80A′, 80B′, metal oxideresist sublayers 80A-80C, and metal oxide resist layer 80. In thedepicted embodiment, the second density, the fourth density, and thefifth density (i.e., densities of the metal-and-oxygen comprising resistmaterials after each cycle) are different, such that metal oxide resistlayer 80 has a density that increases from top to bottom. In someembodiments, the first density, the third density, and the fifth density(i.e., densities of the metal-and-oxygen comprising resist materialsas-deposited) are substantially the same. In some embodiments, the firstdensity, the third density, and/or the fifth density are different. Insome embodiments, the first density, the third density, and/or the fifthdensity are the same as the density of metal oxide resist layer 30.

Sometimes, during an exposure process, unintentional chemical reactions(e.g., crosslinking) occur in unexposed portions of a resist layer. Thisphenomenon may be observed in lithography process A, as depicted in FIG.3A, where chemical reactions undesirably and unintentionally occur inportions of metal oxide resist layer 30 covered by mask 60 (i.e.,unexposed portions 30U), thereby forming unintentionally exposedportions UE that are partially insoluble (instead of soluble) to adeveloper. As a result, unexposed portions 30U are not completelyremoved by the developer, leaving resist remnants S in unexposed areasof workpiece 10. Resist remnants S correspond with unintentionallyexposed portions UE, which can be resist scum (e.g., resist remnantsthat prevent areas of material layer 20 from being patterned) and/orresist footing (e.g., resist remnants at bottoms of exposed portions30E, which cause critical dimension variations and/or LER/LWRvariations). Lithography process D, depicted in FIG. 3A, implements acyclic metal resist deposition process C to provide a metal oxide resistlayer 100 that accounts for and minimizes such phenomenon.

Metal oxide resist layer 100 has a gradient density that increases frombottom to top, such as from a bottom surface of metal oxide layer 100(e.g., interfacing with material layer 20) to a top surface of metaloxide resist layer 100. For example, cyclic metal resist depositionprocess C forms a metal oxide resist sublayer 100A, a metal oxide resistsublayer 100B, and a metal oxide resist sublayer 100C, which combine toform metal oxide resist layer 100 having thickness T. In contrast tometal oxide resist layer 40 (where metal oxide resist sublayers 40A-40Dhave substantially the same densities), a density of metal oxide resistsublayer 100A is less than a density of metal oxide resist sublayer100B, and a density of metal oxide resist sublayer 100B is less than adensity of metal oxide resist sublayer 100C, such that density of metaloxide resist layer 100 increases from bottom to top. Configuring metaloxide resist layer 100 with a low-density bottom portion (i.e., metaloxide resist sublayer 100A) decreases absorption of exposure photons bythe bottom portion of the metal oxide resist layer 100 and thus reducesfrequency of unintended chemical reactions in unexposed portions ofmetal oxide resist layer 100. Configuring metal oxide resist layer 100with a high-density top portion (i.e., metal oxide resist sublayer 100Band metal oxide resist sublayer 100C) increases absorption of exposurephotons by the top portion of the metal oxide resist layer 100. Thegradient density of metal oxide resist layer 100 thus decreasescrosslinking in the bottom portion of the metal oxide resist layer 100while increasing crosslinking in the top portion of the metal oxideresist layer 100. For example, during the exposure process, an amount ofchemical reactions (e.g., crosslinking) in bottom portions of exposedportions 100E may be less than an amount of chemical reactions in topportions of exposed portions 100E, thereby reducing a frequency ofunintentional chemical reactions, such as partial crosslinking, inunexposed portions 100U adjacent to bottom portions of exposed portions100E. As a result, after development, a resist pattern is provided by apatterned metal oxide resist layer 100′ having openings 102 defined bywell-defined exposed portions 100E with minimal to no resist remnants,thereby improving pattern fidelity. In some embodiments, such asdepicted, exposed portions 100E have substantially parallel sidewalls,and widths of exposed portions 100E are substantially the same from topto bottom. In some embodiments, the low-density bottom portion of metaloxide resist layer 100 has a loose, random, and/or non-uniform atomicstructure and the high-density top portion of metal oxide resist layer100 has a dense, ordered, and/or uniform atomic structure.

In some embodiments, an overall density (e.g., average density) of metaloxide resist layer 100 is greater than an overall density (e.g., averagedensity) of metal oxide resist layer 30, such that metal oxide resistlayer 100 can absorb more radiation than metal oxide resist layer 30when exposed to the same exposure dose and absorb such radiation moreuniformly than metal oxide resist layer 30. In the depicted embodiment,the density of metal oxide resist sublayer 100C and the density of metaloxide resist sublayer 100B are greater than the density of metal oxideresist layer 30, while the density of metal oxide resist sublayer 100Ais substantially the same or less than the density of metal oxide resistlayer 30. In furtherance of the depicted embodiment, the density ofmetal oxide resist sublayer 100C is greater than the density of metaloxide resist sublayer 100B. In some embodiments, the density of metaloxide resist sublayer 100C and the density of metal oxide resistsublayer 100B are substantially the same. In some embodiments, densitiesof metal oxide resist sublayers 100A-100C are all greater than thedensity of metal oxide resist layer 30. Metal oxide sublayers 100A-100Ccan have respective density profiles, such as a substantially uniformdensity throughout, a gradient density that increase or decreases from abottom surface to a top surface, an alternating density, or othersuitable density profile. In the depicted embodiment, each of metaloxide sublayers 100A-100C has a substantially uniform density. In someembodiments, an atomic structure of metal oxide resist sublayer 100A isless ordered and/or closely packed than an atomic structure of metaloxide resist sublayer 100B, and an atomic structure of metal oxideresist sublayer 100B is less ordered and/or closely packed than anatomic structure of metal oxide resist sublayer 100C. Metal oxide resistsublayers 100A-100C respectively have a thickness t8, a thickness t9,and a thickness t10, where a sum of thickness t8, thickness t9, andthickness t10 is equal to target thickness T. In the depictedembodiment, thickness t8, thickness t9, and thickness t10 aresubstantially the same. In some embodiments, thickness t8, thickness t9,and/or thickness t10 are different and/or the same depending on desireddensity profile and/or density characteristics.

FIG. 3B illustrates cyclic metal resist deposition process C accordingto various aspects of the present disclosure. In FIG. 3B, cyclic metalresist deposition process C includes three cycles, where each cycleforms one of metal oxide resist sublayers 100A-100C, each cycle includesa deposition process, and some cycles include a densification process.For example, cyclic metal resist deposition process C includes a cycle1, a cycle 2, and a cycle 3. Cycle 1 includes performing a depositionprocess 110-1 to form metal oxide resist sublayer 100A having thicknesst8 and a first density on material layer 20. No densification process isperformed during cycle 1. Cycle 2 includes performing a depositionprocess 110-2 to form a metal oxide resist sublayer 100B′ havingthickness t9 and a second density on metal oxide resist sublayer 100Aand performing a densification process 112-1 on metal oxide resistsublayer 100B′, thereby forming metal oxide resist sublayer 100B havinga third density greater than the second density and the first density ofmetal oxide resist sublayer 100A. Cycle 3 includes performing adeposition process 110-3 to form metal oxide resist sublayer 100C′having thickness t10 and a fourth density and performing a densificationprocess 112-2 on metal oxide resist sublayer 100C′, thereby formingmetal oxide resist sublayer 100C having a fifth density greater than thefourth density and the third density of metal oxide resist sublayer100B. Deposition processes 110-1-110-3 are similar to depositionprocesses 50-1-50-4 described above, densification processes 112-1,112-2 are similar to densification processes 52-1-52-4, and parametersof deposition processes 110-1-110-3 and densification processes 112-1,112-2 can be configured to achieve desired density profiles and/ordesired density characteristics of metal oxide resist sublayers 100B′,100C′, metal oxide resist sublayers 100A-100C, and metal oxide resistlayer 100. In the depicted embodiment, the first density, the thirddensity, and the fifth density (i.e., densities of the metal-and-oxygencomprising resist materials after each cycle) are different, such thatmetal oxide resist layer 100 has a density that decreases from top tobottom. In some embodiments, the third density and the fifth density arethe same, but different and greater than the first density. In someembodiments, the first density, the second density, and the fourthdensity (i.e., densities of the metal-and-oxygen comprising resistmaterials as-deposited) are substantially the same. In some embodiments,the first density, the second density, and/or the fourth density aredifferent. In some embodiments, the first density, the second density,and/or the fourth density are the same as the density of metal oxideresist layer 30.

FIG. 4 illustrates a cyclic metal resist deposition process D forforming a metal oxide resist layer 120 that can be used in a lithographyprocess to improve pattern fidelity according to various aspects of thepresent disclosure. Metal oxide resist layer 120 has an alternatingdensity from bottom to top (e.g., loose-dense-loose-dense), such as froma bottom surface of metal oxide layer 120 (e.g., interfacing withmaterial layer 20) to a top surface of metal oxide resist layer 120. Forexample, cyclic metal resist deposition process D forms a metal oxideresist sublayer 120A, a metal oxide resist sublayer 120B, a metal oxideresist sublayer 120C, and a metal oxide resist sublayer 120D, whichcombine to form metal oxide resist layer 120 having thickness T. Metaloxide resist sublayers 120A-120D respectively have a thickness t11, athickness t12, a thickness t13, and a thickness t14, where a sum ofthickness t11, thickness t12, thickness t13, and thickness t14 is equalto target thickness T. In contrast to metal oxide resist layer 40 (wheremetal oxide resist sublayers 40A-40D have substantially the samedensities), a density of metal oxide resist sublayer 120B is greaterthan a density of metal oxide resist sublayer 120A, a density of metaloxide resist sublayer 120C is less than a density of metal oxide resistsublayer 120B, and a density of metal oxide resist sublayer 120D isgreater than a density of metal oxide resist sublayer 120C, such thatdensity of metal oxide resist layer 120 alternates low-high and/or anatomic structure of metal oxide resist layer 120 alternates loose-densefrom bottom to top. An alternating density profile can balance variouspatterning concerns to optimize pattern fidelity. For example,configuring metal oxide resist layer 120 with a low-density bottomportion (i.e., metal oxide resist sublayer 120A) reduces resist scumand/or resist footing defects, while configuring metal oxide resistlayer 120 with a high-density top portion (i.e., metal oxide resistsublayer 120D) minimizes outgassing and thus outgassing contaminationarising from metal oxide resist layer 120. Further, configuring metaloxide resist layer 120 with a gradient density middle portion thatdecreases from top to bottom (i.e., metal oxide resist sublayer 120B andmetal oxide resist sublayer 120C) can enhance absorption of radiation,thereby improving LER/LWR and/or critical dimension uniformity.

In some embodiments, an overall density (e.g., average density) of metaloxide resist layer 120 is greater than an overall density (e.g., averagedensity) of metal oxide resist layer 30, such that metal oxide resistlayer 120 can absorb more radiation than metal oxide resist layer 30when exposed to the same exposure dose and absorb such radiation moreuniformly than metal oxide resist layer 30. In the depicted embodiment,the densities of metal oxide resist sublayers 120B-120D are greater thanthe density of metal oxide resist layer 30, while the density of metaloxide resist sublayer 120A is substantially the same or less than thedensity of metal oxide resist layer 30. In some embodiments, the densityof metal oxide resist sublayer 120D is a maximum density of metal oxideresist layer 120, the density of metal oxide resist sublayer 120A is aminimum density of metal oxide resist layer 120, and the density ofmetal oxide resist sublayer 120C is between the maximum density and theminimum density. In some embodiments, the density of metal oxide resistsublayer 120B is the same as the density of metal oxide resist sublayer120D. In some embodiments, the density of metal oxide resist sublayer120B is less than the density of metal oxide resist sublayer 120D butgreater than the density of metal oxide resist sublayer 120C. In someembodiments, densities of metal oxide resist sublayers 120A-120D are allgreater than the density of metal oxide resist layer 30. Metal oxidesublayers 120A-120D can have respective density profiles, such as asubstantially uniform density throughout, a gradient density thatincrease or decreases from a bottom surface to a top surface, analternating density, or other suitable density profile. In the depictedembodiment, each of metal oxide sublayers 120A-120D has a substantiallyuniform density.

In FIG. 4 , cyclic metal resist deposition process D includes fourcycles, where each cycle forms one of metal oxide resist sublayers120A-120D, each cycle includes a deposition process, and some cyclesinclude a densification process. For example, cyclic metal resistdeposition process D includes a cycle 1, a cycle 2, a cycle 3, and acycle 4. Cycle 1 includes performing a deposition process 130-1 to formmetal oxide resist sublayer 120A having thickness t11 and a firstdensity on material layer 20. No densification process is performedduring cycle 1. Cycle 2 includes performing a deposition process 130-2to form a metal oxide resist sublayer 120B′ having thickness t12 and asecond density on metal oxide resist sublayer 120A and performing adensification process 132-1 on metal oxide resist sublayer 120B′,thereby forming metal oxide resist sublayer 120B having a third densitygreater than the second density and the first density of metal oxideresist sublayer 120A. Thickness t12 is greater than thickness t11. Cycle3 includes performing a deposition process 130-3 to form metal oxideresist sublayer 120C′ having thickness t13 and a fourth density andperforming a densification process 132-2 on metal oxide resist sublayer120C′, thereby forming metal oxide resist sublayer 120C having a fifthdensity greater than the fourth density and less than the third densityof metal oxide resist sublayer 120B. Thickness t13 is less thanthickness t12 and greater than thickness t11. Cycle 4 includesperforming a deposition process 130-4 to form metal oxide resistsublayer 120D′ having thickness t14 and a sixth density and performing adensification process 132-3 on metal oxide resist sublayer 120D′,thereby forming metal oxide resist sublayer 120D having a seventhdensity greater than the sixth density and greater than the fifthdensity of metal oxide resist sublayer 120C. Thickness t14 is less thanthickness t13. In the depicted embodiment, the seventh density issubstantially the same as the third density. Deposition processes130-1-130-4 are similar to deposition processes 50-1-50-4 describedabove, densification processes 132-1-132-3 are similar to densificationprocesses 52-1-52-4, and parameters of deposition processes 130-1-130-4and densification processes 132-1-132-3 can be configured to achievedesired density profiles and/or desired density characteristics of metaloxide resist sublayers 120B′-120D′, metal oxide resist sublayers120A-120D, and metal oxide resist layer 120. In the depicted embodiment,the first density, the third density, the fifth density, and the seventhdensity (i.e., densities of the metal-and-oxygen comprising resistmaterials after each cycle) are different, such that metal oxide resistlayer 120 has a density that varies from top to bottom. In someembodiments, the first density, the second density, the fourth density,and/or the sixth density (i.e., densities of the metal-and-oxygencomprising resist materials as-deposited) are substantially the same. Insome embodiments, the first density, the second density, and/or thefourth density are different. In some embodiments, the first density,the second density, the fourth density, and/or the sixth density are thesame as the density of metal oxide resist layer 30. FIG. 4 has beensimplified for the sake of clarity to better understand the inventiveconcepts of the present disclosure. Additional features can be added incyclic metal resist deposition process D, and some of the featuresdescribed below can be replaced, modified, or eliminated in otherembodiments of cyclic metal resist deposition process D.

FIG. 5 illustrates a cyclic metal resist deposition process E forforming a metal oxide resist layer that can be used in a lithographyprocess to improve pattern fidelity according to various aspects of thepresent disclosure. Cyclic metal resist deposition process E is similarto cyclic metal resist deposition process A, except cyclic metal resistdeposition process E forms a metal oxide resist layer 140 and tunesdensification processes to induce partial crosslinking in metal oxideresist layer 140. For example, metal oxide resist layer 140 isuniformly, partially crosslinked from bottom to top, such as from abottom surface of metal oxide layer 140 (e.g., interfacing with materiallayer 20) to a top surface of metal oxide resist layer 140. A degree ofcrosslinking in metal oxide resist layer 140 is greater than a degree ofcrosslinking in metal oxide resist layer 30 (which may be zero), suchthat metal oxide resist layer 140 can be patterned with a smallerexposure dose than required for metal oxide resist layer 30. In FIG. 5 ,cyclic metal resist deposition process E forms a metal oxide resistsublayer 140A, a metal oxide resist sublayer 140B, a metal oxide resistsublayer 140C, and a metal oxide resist sublayer 140D, which combine toform metal oxide resist layer 140 having thickness T. Metal oxide resistsublayers 140A-140D respectively have thickness t1, thickness t2,thickness t3, and thickness t4, where a sum of thickness t1, thicknesst2, thickness t3, and thickness t4 is equal to target thickness T. Adegree of partial crosslinking in metal oxide resist sublayer 140A, adegree of partial crosslinking in metal oxide resist sublayer 140B, adegree of partial crosslinking in metal oxide resist sublayer 140C, anda degree of partial crosslinking in metal oxide resist sublayer 140D aresubstantially the same. In the depicted embodiment, thickness t1,thickness t2, thickness t3, and thickness t4 are substantially the same.In some embodiments, thickness t1, thickness t2, thickness t3, and/orthickness t4 are different or the same depending on desired partialcrosslinking profile. FIG. 5 has been simplified for the sake of clarityto better understand the inventive concepts of the present disclosure.Additional features can be added in cyclic metal resist depositionprocess E, and some of the features described below can be replaced,modified, or eliminated in other embodiments of cyclic metal resistdeposition process E.

In FIG. 5 , cyclic metal resist deposition process E includes fourcycles, where each cycle forms one of metal oxide resist sublayers140A-140D and each cycle includes a deposition process and adensification process. For example, cyclic metal resist depositionprocess E includes a cycle 1, a cycle 2, a cycle 3, and a cycle 4, wherecycles 1-4 include deposition processes 50-1-50-4 that form metal oxideresist sublayers 40A′-40D′, respectively, as described above withreference to FIGS. 1A-1C. Cycle 1 includes performing a densificationprocess 152-1 to induce crosslinking in metal oxide resist sublayer40A′, thereby providing metal oxide resist sublayer 140A having a firstdegree of crosslinking. Cycle 2 includes performing a densificationprocess 152-2 to induce crosslinking in metal oxide resist sublayer40B′, thereby providing metal oxide resist sublayer 140B having a seconddegree of crosslinking. Cycle 3 includes performing a densificationprocess 152-3 to induce crosslinking in metal oxide resist sublayer40C′, thereby providing metal oxide resist sublayer 140C having a thirddegree of crosslinking. Cycle 4 includes performing a densificationprocess 152-4 to induce crosslinking in metal oxide resist sublayer40D′, thereby providing metal oxide resist sublayer 140D having a fourthdegree of crosslinking. The first degree, the second degree, the thirddegree, and the fourth degree of crosslinking are less than completecrosslinking. In the depicted embodiment, the first degree, the seconddegree, the third degree, and the fourth degree of crosslinking aresubstantially the same, which can be achieved by tuning parameters ofdensification processes 152-1-152-4. In some embodiments, the firstdegree, the second degree, the third degree, and the fourth degree ofcrosslinking are different and/or the same to achieve metal oxide resistlayer having different crosslinking profiles. In some embodiments, metaloxide resist layer 140 has a degree of crosslinking that varies from topto bottom. For example, the first degree of crosslinking is greater thanthe second degree, the third degree, and/or the fourth degree ofcrosslinking. Densification processes 152-1-152-4 are similar todensification processes described above. For example, densificationprocesses 152-1-152-4 can be soft bakes, UV treatments, IR treatments,other suitable treatments, or combinations thereof.

After performing the various lithography processes described herein(e.g., lithography process A, lithography process B, lithography processC, and/or lithography process D), a fabrication process is performed onworkpiece 10, such as material layer 20 and/or wafer 15, using thepatterned metal oxide resist layers described herein (e.g., patternedmetal oxide resist layer 30′, patterned metal oxide resist layer 40′,patterned metal oxide resist layer 80′, patterned metal oxide resistlayer 100′, patterned metal oxide resist layer formed from metal oxideresist layer 120, and/or patterned metal oxide resist layer formed frommetal oxide resist layer 140) as masks. For example, the fabricationprocess is applied only to portions of workpiece 10 within openings ofthe patterned metal oxide resist layers, while other portions ofworkpiece 10 covered by the patterned metal oxide resist layers (forexample, by exposed portions of the patterned metal oxide resist layers)are protected from the fabrication process. In some embodiments, thefabrication process includes etching material layer 20 using thepatterned metal oxide resist layers as etching masks. A pattern is thustransferred from the patterned metal oxide resist layers to materiallayer 20, thereby forming a patterned material layer. In embodimentswhere material layer 20 is a hard mask layer, the pattern is firsttransferred from the patterned metal oxide resist layers to materiallayer 20, and then the pattern is transferred from the patternedmaterial layer 20 to a material layer of wafer 15. In some embodiments,the fabrication process includes performing an implantation process onmaterial layer 20 using the patterned metal oxide resist layers as animplant mask, thereby forming various doped features (regions) inmaterial layer 20. In some embodiments, the fabrication process includesdepositing a material over material layer 20 using the patterned metaloxide resist layers as a deposition mask, thereby forming variousmaterial features (e.g., gates and/or contacts) over material layer 20.Thereafter, the patterned metal oxide resist layers are removed fromworkpiece 10 using any suitable process. In some embodiments, thepatterned metal oxide resist layers may be partially consumed during thefabrication process, such as during the etching process, such that anyremaining portion of the patterned metal oxide resist layers aresubsequently removed by a suitable process.

The present disclosure provides metal oxide resist layers, cyclic metaloxide resist deposition processes for forming the metal oxide resistlayers, and lithography techniques that implement the metal oxide resistlayers to improve lithography resolution and/or resist pattern fidelity.The present disclosure contemplates that the cyclic metal oxide resistdeposition processes described herein can be implemented to form anytype of metal-comprising resist layer, such as a metal nitride resistlayer, a metal carbide resist layer, and/or any other type ofphotosensitive layer that includes metal. In such embodiments,references to oxygen/oxide can be replaced with references to otherconstituents, such as nitrogen/nitride, carbon/carbide, and/or othermetal-comprising resist constituent. In such embodiments, themetal-comprising resist layers may or may not include oxygen. Theadvanced lithography processes, methods, and materials described abovecan be used in many applications, including FinFETs and/or GAAtransistors. For example, fins may be patterned to produce a relativelyclose spacing between features, for which the above disclosure is wellsuited. In addition, spacers used in forming fins, also referred to asmandrels, can be processed according to the above disclosure.

An exemplary method includes forming a metal oxide resist layer over aworkpiece by performing deposition processes to form metal oxide resistsublayers of the metal oxide resist layer over the workpiece andperforming a densification process on at least one of the metal oxideresist sublayers. Each deposition process forms a respective one of themetal oxide resist sublayers. The densification process increases adensity of the at least one of the metal oxide resist sublayers.Parameters of the deposition processes and/or parameters of thedensification process can be tuned to achieve different densityprofiles, different density characteristics, and/or different absorptioncharacteristics to optimize patterning of the metal oxide resist layer.In some embodiments, forming the metal oxide resist layer furtherincludes performing a purge process after performing the densificationprocess. In some embodiments, the deposition processes and thedensification process are performed in a same process chamber. In someembodiments, performing the densification process includes exposing theat least one of the metal oxide resist sublayers to plasma. In someembodiments, performing the densification process includes soft bakingthe at least one of the metal oxide resist sublayers. In someembodiments, performing the densification process includes exposing theat least one of the metal oxide resist sublayers to ultraviolet (UV)radiation. In some embodiments, performing the densification processincludes exposing the at least one of the metal oxide resist sublayersto infrared (IR) radiation. In some embodiments, the densificationprocess is performed after each deposition cycle, such that each of themetal oxide resist sublayers is subjected to a respective densificationtreatment. In some embodiments, the method further includes tuningdeposition parameters of the deposition processes, tuning densificationparameters of the densification process, or both to achieve a gradientdensity in the metal oxide resist layer. In some embodiments, the methodfurther includes performing an exposure process on the metal oxideresist layer and performing a development process on the metal oxideresist layer, thereby forming a patterned metal oxide resist layer overthe workpiece.

Another exemplary method includes receiving a workpiece in a processchamber; performing, in the process chamber, at least two depositionprocesses to form a metal oxide resist layer over the workpiece; andperforming, in the process chamber, a treatment process to modify adensity profile of the metal oxide resist layer. In some embodiments,the treatment process is performed after each of the at least twodeposition processes, such that the metal oxide resist layer has auniform density from bottom to top. In some embodiments, the treatmentprocess is performed after each of the at least two depositionprocesses, such that the metal oxide resist layer has a varying densityfrom bottom to top. In some embodiments, the treatment process isperformed after at least one of the at least two deposition processes,such that the metal oxide resist layer has a gradient density thatincreases from bottom to top. In some embodiments, the treatment processis performed after at least one of the at least two depositionprocesses, such that the metal oxide resist layer has a gradient densitythat decreases from bottom to top. In some embodiments, the treatmentprocess is performed after at least one of the at least two depositionprocesses, such that the metal oxide resist layer has an alternatingdensity.

An exemplary metal oxide resist layer includes a first metal oxideresist sublayer, a second metal oxide resist sublayer disposed over thefirst metal oxide resist sublayer, a third metal oxide resist sublayerdisposed over the second metal oxide resist sublayer. The first metaloxide resist sublayer has a first density, the second metal oxide resistsublayer has a second density, and the third metal oxide resist sublayerhas a third density. In some embodiments, the first density, the seconddensity, and the third density are substantially the same. In someembodiments, the first density, the second density, and the thirddensity are different. In some embodiments, the first density, thesecond density, and the third density are configured to provide themetal oxide resist layer with a gradient density from the first metaloxide resist sublayer to the third metal oxide resist sublayer.

Another exemplary method includes forming a metal oxide resist layerover a workpiece by performing a deposition process that includes morethan one deposition cycle, such that the metal oxide resist layerincludes a stack of metal oxide resist sublayers, and performing adensification process on at least one of the metal oxide resistsublayers, wherein the densification process increases a density of theat least one of the metal oxide resist sublayers. In some embodiments,the deposition process and the densification process are performed in asame process chamber. In some embodiments, performing the densificationprocess includes exposing the at least one of the metal oxide resistsublayers to a plasma. In some embodiments, performing the densificationprocess includes exposing the at least one of the metal oxide resistsublayers to an annealing process. In some embodiments, performing thedensification process includes exposing the at least one of the metaloxide resist sublayers to ultraviolet (UV) radiation. In someembodiments, performing the densification process includes exposing theat least one of the metal oxide resist sublayers to infrared (IR)radiation. In some embodiments, the deposition process is a chemicalvapor deposition process, an atomic layer deposition process, or acombination thereof. In some embodiments, the densification process isperformed after each deposition cycle, such that each of the metal oxideresist sublayers of the stack of metal oxide resist sublayers issubjected to a respective densification treatment. In some embodiments,the method further includes tuning the performing of the depositionprocess, tuning the performing of the densification process, or both toachieve a gradient density in the metal oxide resist layer. In someembodiments, a first density of a topmost metal oxide resist sub-layerof the stack of metal oxide resist sublayers is greater than a seconddensity of a bottommost metal oxide resist sub-layer of the stack ofmetal oxide resist sublayers. In some embodiments, a first density of atopmost metal oxide resist sub-layer of the stack of metal oxide resistsublayers is less than a second density of a bottommost metal resistoxide sub-layer of the stack of metal oxide resist sublayers. In someembodiments, tuning the performing of the deposition process includesadjusting a precursor gas, a precursor gas flow, a deposition pressure,a deposition temperature, a deposition power, a deposition time, otherdeposition parameter, or a combination thereof. In some embodiments,tuning the performing of the densification process includes adjusting atreatment time, a treatment power, a treatment temperature, othertreatment parameter, or a combination thereof. In some embodiments, themethod further includes tuning the performing of the deposition process,tuning the performing of the densification process, or both to achievean alternating density pattern in the stack of metal oxide resistsublayers. In some embodiments, the method further includes performing apurge process after the performing the densification process. In someembodiments, the densification process is a first densification process,and the method further includes performing a second densificationprocess before the forming the metal oxide resist layer over theworkpiece. In some embodiments, the method further includes performingan exposure process on the metal oxide resist layer and performing adevelopment process on the metal oxide resist layer, thereby forming apatterned metal oxide resist layer over the workpiece. In someembodiments, the densification process is a first densification process,and the method further includes performing the exposure process includesexposing the metal oxide resist layer to patterned extreme ultraviolet(EUV) radiation. In some embodiments, the method further includesperforming an etching process, an implantation process, or a depositionprocess on the workpiece using the patterned metal oxide resist layer asan etch mask, an implantation mask, or a deposition mask, respectively.In some embodiments, the method includes removing the patterned metaloxide resist layer after the etching process, the implantation process,or the deposition process. In some embodiments, the method furtherincludes transferring a pattern in the patterned metal oxide resistlayer to a sacrificial layer disposed over the workpiece, therebyforming a patterned sacrificial layer, and transferring a pattern in thepatterned sacrificial layer to a material layer of the workpiece. Insome embodiments, the method further includes performing a densificationprocess on the workpiece before forming the metal oxide resist layer.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A metal oxide resist layer comprising: a firstmetal oxide resist sublayer having a first density; a second metal oxideresist sublayer disposed over the first metal oxide resist sublayer,wherein the second metal oxide resist sublayer has a second density; anda third metal oxide resist sublayer disposed over the second metal oxideresist sublayer, wherein the third metal oxide resist sublayer has athird density.
 2. The metal oxide resist layer of claim 1, wherein thefirst density, the second density, and the third density aresubstantially the same.
 3. The metal oxide resist layer of claim 1,wherein the first density, the second density, and the third density aredifferent.
 4. The metal oxide resist layer of claim 1, wherein the firstdensity, the second density, and the third density are configured toprovide the metal oxide resist layer with a gradient density from thefirst metal oxide resist sublayer to the third metal oxide resistsublayer.
 5. The metal oxide resist layer of claim 1, wherein the firstdensity and the third density are each less than the second density. 6.The metal oxide resist layer of claim 1, wherein the first density andthe third density are each greater than the second density.
 7. The metaloxide resist layer of claim 1, wherein each of the first metal oxideresist sublayer, the second metal oxide resist sublayer, and the thirdmetal oxide resist sublayer have an atomic structure that includesmetal-and-oxygen constituents stacked in an ordered arrangement.
 8. Themetal oxide resist layer of claim 7, wherein the metal-and-oxygenconstituents include 12-MeO_(x) clusters, 8-MeO_(x) clusters, 6-MeO_(x)clusters, 4-MeO_(x) clusters, dimer-MeO_(x) clusters, mono-MeO_(x)clusters, or a combination thereof, wherein Me is metal, O is oxygen,and x is a number of oxygen atoms.
 9. A metal oxide resist layercomprising: a first metal oxide photosensitive material, a second metaloxide photosensitive material, and a third metal oxide photosensitivematerial sequentially stacked; wherein the first metal oxidephotosensitive material has a first density, the second metal oxidephotosensitive material has a second density, and the third metal oxidephotosensitive material has a third density, wherein the first densityis different than the second density and the second density is differentthan the third density; and wherein the first metal oxide photosensitivematerial has a first thickness, the second metal oxide photosensitivematerial has a second thickness, and the third metal oxidephotosensitive material has a third thickness.
 10. The metal oxideresist layer of claim 9, wherein the first density is greater than thesecond density, and the second density is greater than the thirddensity.
 11. The metal oxide resist layer of claim 9, wherein the firstdensity is less than the second density, and the second density is lessthan the third density.
 12. The metal oxide resist layer of claim 9,wherein the first density is less than the second density, and thesecond density is greater than the third density.
 13. The metal oxideresist layer of claim 9, wherein the first density is greater than thesecond density, and the second density is less than the third density.14. The metal oxide resist layer of claim 9, wherein the first densityis less than the second density and the third density.
 15. The metaloxide resist layer of claim 9, wherein concentrations of metal oxideclusters in the first metal oxide photosensitive material, the secondmetal oxide photosensitive material, and the third metal oxidephotosensitive material are different to provide the first density, thesecond density, and the third density.
 16. The metal oxide resist layerof claim 9, wherein the first thickness, the second thickness, and thethird thickness are different.
 17. A metal oxide resist layercomprising: a photosensitive metal oxide material having an atomicstructure that includes metal-and-oxygen (MeO) constituents stacked inan ordered arrangement; and wherein the photosensitive metal oxidematerial has at least two different densities along a thickness of thephotosensitive metal oxide material.
 18. The metal oxide resist layer ofclaim 17, wherein the metal-and-oxygen constituents include metal oxideclusters, and a first concentration of the metal oxide clusters at abottom of the photosensitive metal oxide material is different than asecond concentration of the metal oxide clusters at a top of thephotosensitive metal oxide material to provide the photosensitive metaloxide material with the at least two different densities along thethickness.
 19. The metal oxide resist layer of claim 17, wherein a firstdensity at a top of the photosensitive metal oxide material is greaterthan a second density at a bottom of the photosensitive metal oxidematerial.
 20. The metal oxide resist layer of claim 17, wherein themetal is Sn, Bi, Sb, In, Te, Ti, Zr, Hf, V, Co, Mo, W, Al, Ga, Si, Ge,P, As, Y, La, Ce, or Lu.